Generally, it is necessary to provide internal cooling of turbine components. To achieve high performance it is desirable to utilise high turbine entry temperatures and so greater thermal efficiencies. Unfortunately, such high turbine entry temperatures are limited by inherent characteristics of the materials from which turbine blades and vanes are made. In such circumstances, internal cooling allows components made from available materials to operate at temperatures which exceed natural melting temperatures.
Cooling systems for turbine vanes and blades generally comprise providing a feed of cool air taken such that there is a positive pressure from the compressor system in a jet engine and feeding that cool air to the turbine blades through internal passages and chambers in order to effect cooling by a combination of internal convection and external film cooling. The present invention principally relates to internal convection cooling where a pressurised passage of coolant air as described previously incorporates a number of flow or injection cross passages to cooling chambers in the vane or blade in order to provide cooling. The cool air is forced into the cooling chambers or other passages of the blade or vane due to a pressure differential between the coolant supply passage and those cooling chambers. The cooler air presented within the chambers or other passages picks up heat by convection within the chamber or passage. The warmed air is then either exhausted through an outlet passage to an exhaust passageway or returned to the supply passage or possibly released through holes in the blade surface in order to provide film cooling on external surfaces of that blade or vane.
There is an objective to increase the degree of cooling possible with respect to components such as turbine vanes and blades in order that higher thermal efficiencies through higher input temperatures can be achieved whilst using available materials with a melting point below those input temperatures.